It is known with these types of switching device that an electronic voltage analysis is carried out in the area of the power supply or by the power supply in order to activate the switching element as a function of the supply voltage applied and energize the respective user. It is known for such voltage analyses that these collect data for available DC or AC voltages over a defined period in respect of the external supply voltage, to enable an average value to be computed. It is known that DC or AC voltages can be distinguished in that peak values of an AC voltage are higher than the constant value of a comparable DC voltage.
With known devices there is likewise provision for a capacitor to be provided in an input circuit for improving electromagnetic compatibility (EMC). Such a capacitor or electrical energy storage medium is referred to below as the input capacitor. Even if such input capacitors are useful and sometimes necessary for improving EMC characteristics, using them produces the disadvantage of electrical power being stored when the external supply voltage is turned off and of the input capacitor only discharging slowly. The discharge behavior of the input capacitor in its turn influences the data obtained by the voltage analysis. This means that the voltage analysis can result in errors, because for example, as a result of missing zero crossings, a DC voltage is assumed and through the higher peak values too high a voltage is also assumed.
Known approaches attempt to solve this problem in that, for rapid discharging of the input capacitor or of each input capacitor, a resistor is connected in parallel to the input via which the external supply voltage is able to the supplied to the switching device. However this solution results in high power loss or long discharge time constants.